The Methods Core will be led by Drs. Michael VonKorff and Carolyn Rutter. Dr. VonKorff will contribute specific expertise regarding analysis of health care utilization and cost data 6263 and regarding assessment of functional impairment and disability 64-66. Dr. Rutter will contribute specific expertise regarding analysis of complex clustered samples (e.g. clustering of multiple observations within patients and multiple patients under physicians) and provider and patient profiling 6. Other scientists with significant effort devoted to the Methods Core will include Drs. Ludman and Simon. Dr. Ludman will contribute expertise regarding mediators or intermediate outcomes of mood disorder interventions 67 and assessment of patients' experience of care 55. Dr. Simon will contribute specific expertise regarding assessment of mood disorder symptoms and diagnoses 68-70, psychometric methods such as item response theory, and analysis of health care utilization and cost data 6271 .